The purpose of the proposed research is to gain a better understanding of the relations between gonadal hormones and several behaviors as well as the mechanisms by which these hormones act on the brain to affect behavior. The first portion of this program will deal with the effects of sexual and hormonal variables on the behaviors that regulate body weight in laboratory rodents (e.g., eating, exercise, thermoregulation, dietary self-selection). Specific projects will examine the effects of various combinations of brain lesions, endocrinectomies, and steroid treatments (both systemic and intracerebral) on these behaviors. The second portion of this program will attempt to determine the sites and mechanisms of action of gonadal hormones in the brain. Specific experiments will correlate brain uptake of radiolabelled steroids with changes in neural protein synthesis and behavior, when the steroids are administered in the dosages, injection routes and vehicles, and time-courses that affect behavior. It is hoped that this research will contribute to our understanding of the neuroendocrine regulation of body weight, the effects of gonadal hormones on a variety of behaviors, and the actions of steroids on the nervous system. With the current emphasis on the possible role of sex and hormones in human behavior, this research could be of some value and interest.